IBM DS8880 Series, Introduction And Planning Manual

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capacity. However, a reduction in the size of the extent pool can cause the
allocatable physical capacity to become less than the allocated physical capacity in
some cases.
For example, if the user requests that one of the ranks in an extent pool be
depopulated, the data on that rank are moved to the remaining ranks in the pool
causing the rank to become not allocated and removed from the pool. The user is
advised to inspect the limits and threshold on the extent pool following any
changes to the size of the extent pool to ensure that the specified values are still
consistent with the user’s intentions.
IBM Easy Tier
Easy Tier is an optional feature that is provided at no cost. It can greatly increase
the performance of your system by ensuring frequently accessed data is put on
faster storage. Its capabilities include manual volume capacity rebalance, auto
performance rebalancing in both homogeneous and hybrid pools, hot spot
management, rank depopulation, manual volume migration, and thin provisioning
support (ESE volumes only). Easy Tier determines the appropriate tier of storage
that is based on data access requirements and then automatically and
non-disruptively moves data, at the subvolume or sub-LUN level, to the
appropriate tier in the storage system.
Use Easy Tier to dynamically move your data to the appropriate drive tier in your
storage system with its automatic performance monitoring algorithms. You can use
this feature to increase the efficiency of your flash drives and the efficiency of all
the tiers in your storage system.
You can use the features of Easy Tier between three tiers of storage within a
DS8880.
Easy Tier features help you to effectively manage your system health, storage
performance, and storage capacity automatically. Easy Tier uses system
configuration and workload analysis with warm demotion to achieve effective
overall system health. Simultaneously, data promotion and auto-rebalancing
address performance while cold demotion works to address capacity.
Easy Tier data in memory persists in local storage or storage in the peer server,
ensuring the Easy Tier configurations are available at failover, cold start, or Easy
Tier restart.
With Easy Tier Application, you can also assign logical volumes to a specific tier.
This feature can be useful when certain data is accessed infrequently, but needs to
always be highly available.
Easy Tier Application is enhanced by two related functions:
v Easy Tier Application for IBM Z provides comprehensive data-placement
management policy support from application to storage.
v Easy Tier application controls over workload learning and data migration
provides a granular pool-level and volume-level Easy Tier control as well as
volume-level tier restriction where a volume can be excluded from the Nearline
tier.
Chapter 3. Data management features
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